diff --git a/function_test/Makefile b/function_test/Makefile
index a34972cf1441c4171922d1dff94091418d71037f..124e453da6f04995746771798e93ce1a5cadeeb9 100644
--- a/function_test/Makefile
+++ b/function_test/Makefile
@@ -28,7 +28,7 @@ SCRIPTFLAGS += -coverage
 endif
 # Runtime selection
 #RT2 := yes
-ifeq ($(RT2), yes)
+ifdef RT2
 SCRIPTFLAGS += -rt2
 endif
 
diff --git a/function_test/Semantic_Analyser/Makefile.semantic b/function_test/Semantic_Analyser/Makefile.semantic
index 5da604a0d236f316da4cb5dadab512ebf1431caa..dc3b085da045a9809571cebb74f95a079128d901 100644
--- a/function_test/Semantic_Analyser/Makefile.semantic
+++ b/function_test/Semantic_Analyser/Makefile.semantic
@@ -14,7 +14,7 @@
 ##############################################################################
 SADIRS := ver xer encode param template any_from pattern_ref float recof_index \
 port_translation
-ifeq ($(RT2), yes)
+ifdef RT2
 SADIRS += deprecated erroneous_attributes template_concat
 endif
 #$(wildcard TTCN3_[a0-9]* ASN_[a0-9]*) ver xer
diff --git a/function_test/Semantic_Analyser/common.mk b/function_test/Semantic_Analyser/common.mk
index 4ce105e4b688243651f6a4082e08e5488a89b8a9..ad95d6e8ad728ee86e041a4930cea372958582ce 100644
--- a/function_test/Semantic_Analyser/common.mk
+++ b/function_test/Semantic_Analyser/common.mk
@@ -17,7 +17,7 @@
 
 # Flags for the TTCN-3 and ASN.1 compiler:
 COMPILER_FLAGS := -s -g
-ifeq ($(RT2), yes)
+ifdef RT2
 COMPILER_FLAGS += -R
 endif